Aluminum "tin"boat issue

[wtrueman]

Hi all: what I have is my al. 16 foot "tin" boat. If you live on the west coast of Canada you know what I am referring to. Anyway,
I have been using simple 304, I think, 1/4 by one inch stainless to bolt add ons to the boat. My question: can I find al bolts and nuts or should I even worry because I already have zincs to slow down the electrolysis? Thanks for your time, Wayne.

[michigan doug]

Fastenall has a pretty informative site on bimetallic corrosion problems:

https://www.fastenal.com/content/fed...0Corrosion.pdf


You could passivate the stainless with oxalic acid and get some improved corrosion resistance. I had an old timer tell me one time that burying stainless in the damp earth for a week passivates it well. I wouldn't be surprised if there are organic acids, probably including tanic and oxalic stuff....


I also wonder if you could get zinc washers to put under the stainless nuts, if that would help.


How much salt water does it see?


How much cleaning and inspection do you want to do?

[reggie_obe]

McMasterCarr has aluminum machine screws and hex cap bolts.

[Cuttings]

I have worked with stainless fasteners in aluminum masts for a lot of years, and these were all threaded right into the aluminum. The best solution I found was to use liquid Teflon pipe sealer around the fastener and in the threads. The sealer lubricates and seals the thread or connection between the stainless steel and the aluminum. I experienced no corrosion over periods as long as 20 years and the fasteners could be loosened with a screwdriver and removed by hand after a lot of years in the salt environment. Your tin boat might not be as easy, but the idea is to keep the moisture out of the connection.

[Alistair Hosie]

Problem will be if you scratch the surface and remove the zinc coating and expose the steel. If I understand you correctly it will not be tin but steel with a zinc coating correct me if I am wrong. Just remember nothing lasts forever so just keep on top of it and do your best when taking it out of salty water wash it down with clear unsalted water. That always did the one My father in law had many years ago. Alistair

[Mister ED]

Problem will be if you scratch the surface and remove the zinc coating and expose the steel. If I understand you correctly it will not be tin but steel with a zinc coating correct me if I am wrong.

I believe it's actually an aluminum boat. They are commonly referred to over here as tin boats. And when the salmon are running on the Great Lakes, we have the Tin Navy patrolling every port.

All that out of the way, we always use SS fasteners. I will say though, we do not have salt water.

[wtrueman]

Thanks all, stainless will continue to be used, Wayne

[Mike Burch]

In order of preference:
Monel
Passivated 316
Ordinary 316
304
Galvanised.

Aluminium fastenings can be problematic in terms of strength if the size is minimal.

[Forrest Addy]

Big question: salt water?

Aluminum (some alloys anyway) holds up pretty well in salt water so long as no part is in a galvanic couple. Freshwater no sweat. Salt water, I strongly suggest a zinc in the neighborhood particularly in submerged service.

Lots of info in Google.

Here's one that may not apply to your situation but the picture was cool:

http://www.boatingmag.com/protecting...ater-corrosion

[Kiwi]

It all depends on how long you want to keep it most do not bother about electrolysis affecting the boat however if the fittings are below the water line then it would be prudent to insulate especially if it is used a lot in salt water fresh is not as bad and with a motor a 3/8" SS eye bolt going through the steam of a wooden boat a galvanised chain held on with a SS Shackle parted after 12 months in salt water as it was on the water line no anode

[flylo]

Be careful, when I was younger I saw & heard of several steel boat bottoms giving up & sinking. Glad those aren't used anymore here at least.

[darryl]

I'm no expert on this, but when at times I've needed to bolt stuff together on my bike I used stainless hardware and waxed it all with carnuba before assembly. I never saw any corrosion, and never had a problem with anything seizing.

[ezduzit]

Forget about aluminum fasteners. Use stainless. But apply Tef Gel to them when installing.

[wtrueman]

Hi all: What happens is that I put the boat in the water for two to three weeks at a time; used to be six seven weeks but no more, getting too old to weather the whole summer at once! When I come home, it gets washed down or, probably, gets rained off! Lol! Wayne.

[michigan doug]

Yup, just use stainless, your favorite teflon goop and monitor. Should outlast you.